December 31, 2004

Waves, contagion, and the spread of linguistic changes

Labov has found a spreading sound shift in inland Northern cities (Buffalo, Cleveland, Toledo, Chicago, but not Columbus or Indianapolis) stopped dead by a line where the prevailing ideology of Northern Yankees (anti death penalty; pro gun control) ceases to be a typical feature of local political opinion — a sharp and rather unexpected intrusion of ideology on the course of linguistic change.

The image Geoff uses here is like that of a spreading wave, which is halted by natural barriers. But wave trains are not a particularly good metaphor for the spread of linguistic changes. Contagion is another attractive metaphor, but it too is unsatisfactory in most cases. When we look at the micromechanisms at work in the spread of variants, though, the "barrier" effect that Labov observes is not at all surprising (though it's nice to have it illustrated so dramatically).

Quite possibly Labov said this in his MLA talk, but let me say it here anyway.

For a wave to propagate, all it takes is for molecules to be in contact. The molecules that have energy transmitted to them don't have to be receptive to it; they just have to be there. The spread of linguistic variants doesn't have this automatic quality. Merely hearing some variant doesn't cause you to adopt it; you have to be receptive to it.

The contagion metaphor is a bit better, since it incorporates some notion of susceptibility to the disease, which translates in the linguistic case into some kind of receptivity to a new variant. And in some cases -- notably the spread of many lexical items -- this seems to be an adequate picture of the events in question.

But the spread of syntactic, morphological, and phonological variants requires more than contact and simple receptivity to new variants. You have to view yourself as like the people who use the variant, so that you'll be willing to accommodate to their speech to some extent. These variants spread locally, by interaction among companions. Insofar as you don't identify with people -- say, because you hold to very different ideologies -- even if you're in regular contact with them, you're unlikely to adopt their behaviors.